Recently, as energy consumption is increased, solar cells to convert the solar light into electrical energy have been developed.
In particular, a CIGS-based solar cell apparatus, which is a PN hetero junction apparatus having a substrate structure including a glass substrate, a metallic back electrode layer, a P-type CIGS-based light absorbing layer, a high-resistance buffer layer, and an N-type window layer, has been extensively used.
Various studies and researches have been performed to improve electrical characteristics of the solar cell apparatus, such as low resistance and high transmittance.